// Physical memory allocator, intended to allocate
// memory for user processes, kernel stacks, page table pages,
// and pipe buffers. Allocates 4096-byte pages.
#include "kalloc.h"
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "spinlock.h"


void freerange(void *vstart, void *vend);
extern char end[]; // first address after kernel loaded from ELF file

struct run {
  struct run *next;
};


int left_mem;

struct {
  struct spinlock lock;
  int use_lock;
  struct run *freelist;
} kmem;

// Initialization happens in two phases.
// 1. main() calls kinit1() while still using entrypgdir to place just
// the pages mapped by entrypgdir on free list.
// 2. main() calls kinit2() with the rest of the physical pages
// after installing a full page table that maps them on all cores.
void
kinit1(void *vstart, void *vend)
{
  initlock(&kmem.lock, "kmem");
  kmem.use_lock = 0;
  freerange(vstart, vend);

  left_mem = -2;
}

void
kinit2(void *vstart, void *vend)
{

  freerange(vstart, vend);
  kmem.use_lock = 1;

  cprintf("[kinit2]\tvstart=%x\tvend=%x\n", vstart, vend);

  left_mem = -2;
  //cprintf("*** kmem.use_lock = %d", kmem.use_lock);
  //kmem_show("init2");
}

void kmem_show(char *add_txt)
{
  struct run *r;
  int count = 0;

  if(left_mem == -2)
  {
      r = kmem.freelist;
      while(r)
      {
        if(r->next) ;
        else cprintf("[%s]\tkmem\t%x\tr = %p\tcount = %d %s\n",add_txt,&kmem,r,(count*4096)/1024,"KBs");
        r = r->next;
        count ++;
      }
      left_mem = count;
  }
  else
  {
      left_mem --;
      cprintf("[%s]\tkmem\t%x\tleft mem = %d %s\n",add_txt,&kmem,(left_mem*4096)/1024,"KBs");
  }

}

void
freerange(void *vstart, void *vend)
{
  char *p;
  p = (char*)PGROUNDUP((uint)vstart);
  for(; p + PGSIZE <= (char*)vend; p += PGSIZE)
    kfree(p);
}

//PAGEBREAK: 21
// Free the page of physical memory pointed at by v,
// which normally should have been returned by a
// call to kalloc().  (The exception is when
// initializing the allocator; see kinit above.)
void
kfree(char *v)
{
  struct run *r;

  if((uint)v % PGSIZE || v < end || v2p(v) >= PHYSTOP)
    panic("kfree");

  // Fill with junk to catch dangling refs.
  memset(v, 1, PGSIZE);

  if(kmem.use_lock)
    acquire(&kmem.lock);
  r = (struct run*)v;
  r->next = kmem.freelist;
  kmem.freelist = r;
  if(kmem.use_lock)
    release(&kmem.lock);

  //kmem_show("kfree");
    //cprintf("%d", kmem.use_lock);
//  if(left_mem != -2)
//  {
//      left_mem ++;
//  }
}

// Allocate one 4096-byte page of physical memory.
// Returns a pointer that the kernel can use.
// Returns 0 if the memory cannot be allocated.
char*
kalloc(void)
{
  struct run *r;

  if(kmem.use_lock)
    acquire(&kmem.lock);
  r = kmem.freelist;
  if(r)
    kmem.freelist = r->next;
  if(kmem.use_lock)
    release(&kmem.lock);

  //kmem_show("alloc");


  return (char*)r;
}

